Editing Virtual Ethernet device

Virtual ethernet device is ethernet device which can be used inside a [[VE]]. Unlike
venet network device, veth device has a MAC address.

Virtual ethernet device consist of two ethernet devices - one in [[VE0]] and another one 
in VE. These devices are connected to each other, so if a packet goes to one
device it will come out from the other device.


== Virtual ethernet device usage ==

=== Adding veth to a VE ===
<pre>
vzctl set <VEID> --veth_add <dev_name>,<dev_addr>,<ve_dev_name>,<ve_dev_addr>
</pre>
Here 
* <tt>dev_name</tt> is ethernet device name in the [[VE0|host system]]
* <tt>dev_addr</tt> is its MAC address
* <tt>ve_dev_name</tt> is an ethernet device name in the VE
* <tt>ve_dev_addr</tt> is its MAC address

MAC addresses must be entered in XX:XX:XX:XX:XX:XX format. Note that this option
is incremental, so devices are added to already existing ones.

==== Examples ====
<pre>
vzctl set 101 --veth_add veth101.0,00:12:34:56:78:9A,eth0,00:12:34:56:78:9B --save
</pre>
After executing this command <tt>veth</tt> device will be created for VE 101 and veth configuration will be saved to a VE configuration file.
Host-side ethernet device will have <tt>veth101.0</tt> name and <tt>00:12:34:56:78:9A</tt> MAC address.
VE-side ethernet device will have <tt>eth0</tt> name and <tt>00:12:34:56:78:9B</tt> MAC address.
{{Note|Use random MAC addresses. Do not use MAC addresses of real eth devices, beacuse this can lead to collisions.}}

=== Removing veth from a VE ===
<pre>
vzctl set <VEID> --veth_del <dev_name>
</pre>
Here <tt>dev_name</tt> is the ethernet device name in the [[VE0|host system]].

==== Example ====
<pre>
vzctl set 101 --veth_del veth101.0 --save
</pre>
After executing this command veth device with host-side ethernet name veth101.0 will be removed from VE 101 and veth configuration will be updated in VE config file.

== Common configurations with virtual ethernet devices ==
Module <tt>vzethdev</tt> must be loaded to operate with veth devices.

=== Simple configuration with virtual ethernet device ===

==== Start a VE ====
<pre>
[host-node]# vzctl start 101
</pre>

==== Add veth device to VE ====
<pre>
[host-node]# vzctl set 101 --veth_add veth101.0,00:12:34:56:78:9A,eth0,00:12:34:56:78:9B --save
</pre>

==== Configure devices in VE0 ====
<pre>
[host-node]# ifconfig veth101.0 up
[host-node]# echo 1 > /proc/sys/net/ipv4/conf/veth101.0/forwarding
[host-node]# echo 1 > /proc/sys/net/ipv4/conf/veth101.0/proxy_arp
[host-node]# echo 1 > /proc/sys/net/ipv4/conf/eth0/forwarding
[host-node]# echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp
</pre>

==== Configure device in VE ====
<pre>
[host-node]# vzctl enter 101
[ve-101]# /sbin/ifconfig eth0 up
[ve-101]# /sbin/ip addr add 192.168.0.101 dev eth0
[ve-101]# /sbin/ip route add default dev eth0
</pre>

==== Add route in [[VE0]] ====
<pre>
[host-node]# ip route add 192.168.0.101 dev veth101.0
</pre>

=== Virtual ethernet device with IPv6 ===

==== Start [[VE]] ====
<pre>
[host-node]# vzctl start 101
</pre>

==== Add veth device to [[VE]] ====
<pre>
[host-node]# vzctl set 101 --veth_add veth101.0,00:12:34:56:78:9A,eth0,00:12:34:56:78:9B --save
</pre>

==== Configure devices in [[VE0]] ====
<pre>
[host-node]# ifconfig veth101.0 up
[host-node]# echo 1 > /proc/sys/net/ipv6/conf/veth101.0/forwarding
[host-node]# echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding
[host-node]# echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
</pre>

==== Configure device in [[VE]] ====
<pre>
[host-node]# vzctl enter 101
[ve-101]# /sbin/ifconfig eth0 up
</pre>

==== Start router advertisement daemon (radvd) for IPv6 in VE0 ====
First you need to edit radvd configuration file. Here is a simple example of <tt>/etc/radv.conf</tt>:
<pre>
interface veth101.0
{
        AdvSendAdvert on;
        MinRtrAdvInterval 3;
        MaxRtrAdvInterval 10;
        AdvHomeAgentFlag off;

        prefix 3ffe:2400:0:0::/64
        {
                AdvOnLink on;
                AdvAutonomous on;
                AdvRouterAddr off;
        };
};

interface eth0
{
        AdvSendAdvert on;
        MinRtrAdvInterval 3;
        MaxRtrAdvInterval 10;
        AdvHomeAgentFlag off;

        prefix 3ffe:0302:0011:0002::/64
        {
                AdvOnLink on;
                AdvAutonomous on;
                AdvRouterAddr off;
        };
};
</pre>

Then, start radvd:
<pre>
[host-node]# /etc/init.d/radvd start
</pre>

==== Add IPv6 addresses to devices in [[VE0]] ====
<pre>
[host-node]# ip addr add dev veth101.0 3ffe:2400::212:34ff:fe56:789a/64
[host-node]# ip addr add dev eth0 3ffe:0302:0011:0002:211:22ff:fe33:4455/64
</pre>

=== Virtual ethernet devices can be joined in one bridge ===
Perform steps 1 - 4 from Simple configuration chapter for several VEs and/or veth devices

==== Create bridge device ====
<pre>
[host-node]# brctl addbr vzbr0
</pre>

==== Add veth devices to bridge ====
<pre>
[host-node]# brctl addif vzbr0 veth101.0
...
[host-node]# brctl addif vzbr0 veth101.n
[host-node]# brctl addif vzbr0 veth102.0
...
...
[host-node]# brctl addif vzbr0 vethXXX.N
</pre>

==== Configure bridge device ====
<pre>
[host-node]# ifconfig vzbr0 up
[host-node]# echo 1 > /proc/sys/net/ipv4/conf/vzbr0/forwarding
[host-node]# echo 1 > /proc/sys/net/ipv4/conf/vzbr0/proxy_arp
</pre>

==== Add routes in [[VE0]] ====
<pre>
[host-node]# ip route add 192.168.101.1 dev vzbr0
...
[host-node]# ip route add 192.168.101.n dev vzbr0
[host-node]# ip route add 192.168.102.1 dev vzbr0
...
...
[host-node]# ip route add 192.168.XXX.N dev vzbr0
</pre>

Thus you'll have more convinient configuration, i.e. all routes to VEs will be through this bridge and VEs can communicate with each other even without these routes.

=== Virtual ethernet devices + VLAN ===
This configuration can be done by adding vlan device to the previous configuration.

== External links ==
* [http://www.tldp.org/HOWTO/Linux+IPv6-HOWTO/hints-daemons-radvd.html Linux IPv6 HOWTO, a chapter about radvd]


[[Category: Networking]]
[[Category: HOWTO]]